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STRENGTH

One-rep max (1RM) calculator

Estimate a lifting max and work out the plates.

Your completed set

Example values. Edit them to match yours.

kg
reps

Enter a completed set of 1–10 reps. The result is an estimate, not an instruction to lift it.

On your device. No inputs uploaded.

Your lifting estimate

Two equations, percentage loads, and a plate helper.

Ready when you are.

General information and estimates, not medical advice.

Use your result.

01

Use a completed set

Enter a weight and rep count you have actually completed. The estimate depends on the exercise and the effort of that set.

02

Compare, rather than chase

Look at both equations. Their average is a convenient reference, not proof that you can safely lift that exact weight.

03

Keep consistency in view

ACSM’s 2026 guidance emphasises consistency and matching training to the person and goal. A calculator should support a plan, not replace one.

BEHIND THE NUMBERS

Method & trusted reading

An estimate.
Not a challenge.

Use a weight and the repetitions you completed to estimate a one-repetition maximum. An equation cannot measure your strength.

Two estimates

Epley: weight × (1 + reps ÷ 30). Brzycki: weight × 36 ÷ (37 − reps). For a single rep, both equal your entered weight. The main result is their simple average, not a validated improvement in accuracy.

Keep the context

We support 1–10 repetitions. Technique, exercise, fatigue, and how close the set was to your limit affect the estimate. The difference between equations is not a confidence interval.

Percentage loads

The table uses the average estimate, before rounding to actual plates. It is arithmetic, not a training prescription. Use your judgement and appropriate coaching when deciding what to lift.

Formula references

Documented 9 November 2026. No clinical review is claimed.

Read further.

Original research and official guidance. References do not imply endorsement of HandyShelf.

PROFESSIONAL GUIDANCE

ACSM’s 2026 resistance-training update ↗

A current overview of evidence-based resistance training for healthy adults. Read the recommendations in context rather than deriving a programme from one percentage.

American College of Sports MedicineRESEARCH PAPER

Repetitions are not one universal curve ↗

A meta-regression examines how repetitions at a percentage of 1RM vary with factors including exercise and population.

Nuzzo et al. · 2024PUBLIC HEALTH GUIDANCE

Strength is part of a broader routine ↗

The CDC explains how aerobic and muscle-strengthening activity fit together for adults.

Centers for Disease Control and Prevention

Quick questions.

Should I attempt the estimated weight?

The result is not an instruction to attempt a maximum lift. Safe training depends on your experience, technique, environment, and coaching.

Why show two formulas?

They can disagree. We make that visible instead of presenting a model output as a measured fact.

Do kilograms and pounds change the result?

Switching units converts the weight. It does not change the underlying load.